“The Over-current limit load switch project presented here provides full protection to devices and loads from access load conditions. The default current limit is set to 1 Amp, however, this load limit is adjustable from 0.4A to 2A with the help of R4 ISET resistor. When an overload condition occurs circuit responds to that overload condition that lasts longer than a fixed blanking period by turning off the load, followed by a retry after the auto-restart time, auto-retry time is 127.5ms. Flag output is pulled up with R1 and the board provides active low output in a fault condition, normally Flag output is high. Power good output is also pulled up and it’s an open-drain output to indicate that the output voltage has reached 90% of the input voltage. The input range of this circuit is 5V to 24V DC. The load can be activated or deactivated with low-voltage logic compatible on Pin4, jumper J1 is provided to activate or deactivate the output. Close the jumper J1 to activate the output load.
An under-voltage condition on the input or if junction temperature is in excess of 140-degree centigrade overrides the ON control and turns OFF the switch. In addition, an over-current condition causes the switch to turn OFF. After the expiration of the blanking time, the IC has an auto-restart feature that automatically turns the switch ON again after the auto-restart time of 127.5ms.
It is important to choose the appropriate value of resistor R5 and R6 which is dependent on the operating power supply, choose R5 4K7 and R6 3K3 for supply input 5V to 12V, alter these resistors value R5 10K and R6 2K2 ohms for supply input 13V to 24V DC. Voltage ON pin 4 should not exceed 5.5V. Default current limit is set to 1A, refer (I-Set resistor R4) table for the current limit set.
The FPF2700 over current limit switch is designed to meet the power requirements of a variety of applications with a wide input voltage range 2.8V to 36V and adjustable current-limit value. while providing optimum operation current for safe designed practices. The core of the switch is a typical 88mOhms (V=12V)
The N channel MOSFET and controller is capable of functioning over an input voltage range of 2.8V to 36V. FPF offers adjustable current limiting, under-voltage lockout, power-good indicator, fault flag output, and thermal shutdown protection. In the event of an over-current condition, the load switch limits the loads to the current value. The current limit value of the switch can be adjusted from 400mA to 2Amps trough the ISET pin. The enable pin is active LOW for and controls the state of the switch. Pulling the ON pin continuously to LOW holds the switch in on state. The switch moves into the OFF state when the ON pin is pulled HIGH. The ON pin can be pulled HIGH to a maximum voltage 5.5V.”